1. Field of the Invention
The present invention relates to a knob switch apparatus which causes a contact holder to linearly move by means of an arm using the rotational operation of an operation knob. Description of the Related Art
An example of conventional switch apparatuses for wipers in automobiles comprises a spherical pressure portion provided at the end of an arm which is swung by the rotationaloperation of an operational knob provided at the end of a lever, the pressure portion being inserted into a groove of a contact holder. The contact holder is linearly moved by being pressed by the pressure portion of the arm when the operational knob is rotated. The switch is consequently switched corresponding to the movement of the contact holder.
In the above-described conventional arrangement, as shown in FIG. 7, a contact holder is moved along a distance a when an arm 1 is rotated through angle .alpha. in the direction shown by the arrow A from the standard state wherein a pressure portion 2 of the arm 1 points in a vertical direction. When the arm 1 is further rotated through angle .alpha. in the direction shown by the arrow A, the contact holder is also moved along a distance b. Movement distance b is smaller than movement distance a (b&lt;a). That is, there is a disadvantage in that the distance of movement of the contact holder is reduced as the rotation angle of the arm 1 increases even if the operational angle of the operation knob is constant.
Accordingly, it is an object of the present invention to provide a knob switch apparatus which is capable of preventing the difference in movement of a contact holder from being increased due to the difference in the rotational angle of an arm.